Efficient Reduction of Prions by the Manufacturing Process of a VWF/FVIII Product

Variant Creutzfeldt-Jakob disease (vCJD) is a fatal neurodegenerative disease acquired through infection with prions which cause bovine spongiform encephalopathy (BSE) by consumption of beef products from infected cattle. Presumptive transfusion transmitted cases of vCJD have been reported in the UK increasing the concern that medicinal products manufactured from plasma might also pose a risk of vCJD transmission. Therefore, investigational studies were performed to assess the prion reduction capacity of the manufacturing process of a VWF/FVIII product (Haemate^® P / Humate-P^®). In these studies hamster brain derived prion material in the form of a microsomal preparation were used to spike plasma product intermediates. As the purification process of a desired plasma protein may impact the physico-chemical form of the spiked prion protein, the addition of reduction factors from single step studies possibly might not reflect the true prion reduction of the full process; in particular where the spike material is heterogeneous, one fraction, i.e. gross aggregates of prion material could be preferentially removed by one step and the same subfraction by a subsequent step. Therefore, we employed a combined step study approach and not a single spike step approach to address that issue of the impact of heterogeneous spike fractions regarding the overall reduction factor. The manufacturing process of the VWF/FVIII product was divided in two parts which were studied independently twice: Pooled plasma donations (4,500 ml) were spiked and processed covering cryoprecipitation, Al(OH)₃ adsorption and subsequent precipitations by glycine and NaCl. The second part of the VWF/FVIII manufacturing process was studied starting with spiked dissolved NaCl precipitate (154 ml) and processed further by pasteurization, second NaCl precipitation, dialysis, ultracentrifugation and sterile filtration. The prion spiked starting material and product intermediate were processed according to the manufacturing conditions based on a valid down-scale model. The prion reduction factors were determined as the difference of the prion load in the spiked starting materials and in the respective final samples using a biochemical assay (Conformation-Dependent Immunoassay (CDI)) or a bioassay in hamsters for quantification of PrP^Sc (dose dependent incubation period measurement). The results of these investigational studies for the two prion quantification methods are shown below

These results demonstrate (i) comparable prion reduction factors quantified either by biochemical methods or by a bioassay and (ii) an appropriate overall prion reduction capacity of the manufacturing process of Haemate^® P / Humate-P^®. Based on complementary safety procedures, i.e., collection of plasma by stringent donor selection due to geographic donor deferral policy and the overall prion reduction factor of approximately 6 log₁₀, which clearly exceeds a potential prion load in the manufacturing pool, a risk assessment results in an extremely remote risk of prion transmission by the VWF / FVIII product Haemate^® P / Humate-P^®.